We are investigating the circuit which links visual input to escape jumping in grasshoppers. We have identified a chain of neurons extending from the medulla of the optic lobe, through lobula, brain and thoracic ganglia to the jump motor neurons. The probability of a given visual input eliciting a behavioral output (i.e. the jump) is affected by a variety of processes acting at different points of this neural circuit, and especially at optic lobe synapses and at the motorneuron input dendritic fields, and also by such factors as the animals's body temperature. We propose to extend our knowledge of the system by further characterization of circuit elements and processes in both optic lobe and brain, and to investigate the possible interactions with ocellar interneurons, which we have also characterized independently.